In Ubuntu, you may sometimes encounter an error when attempting to run an apt command:

E: Could not get lock /var/lib/dpkg/lock-frontend - open (11: Resource temporarily unavailable)
E: Unable to acquire the dpkg frontend lock (/var/lib/dpkg/lock-frontend), is another process using it?

Pre-requisites

• Access to a terminal window/command line
• A user account with sudo or root privileges

Fix

• Verify apt and/or dpkg isn’t running. It’s still running; then, you should wait for the process to finish.

ps aux | grep -i -E 'apt\|dpkg'

• If the process is stuck using the following.

kill -9 `ps aux | grep -i -E 'apt\|dpkg' | grep -v grep | awk '{print $2}'`

• Remove the lock file.

sudo rm /var/lib/dpkg/lock
sudo rm /var/lib/apt/lists/lock
sudo rm /var/cache/apt/archives/lock